Rats are one of the most widespread and successful mammals on Earth. They have been living alongside humans for thousands of years, and have influenced our history, culture, science, and health in many ways. But how did rats become what they are today? What are the origins and adaptations of these remarkable rodents? In this article, we will explore the fascinating history and evolution of rats, from their ancient ancestors to their modern descendants.
How rats evolved from ancient rodents
Rats belong to the order Rodentia, which is the largest group of mammals, comprising about 40% of all living mammal species. Rodents are characterized by their continuously growing incisors, which they use for gnawing on various materials. The earliest rodents appeared about 66 million years ago, after the Cretaceous-Paleogene extinction event that wiped out most of the dinosaurs and other large animals. These primitive rodents were small, shrew-like creatures that fed on insects and seeds.
Over time, rodents diversified into many different families and subfamilies, occupying various ecological niches and habitats. One of these families is Muridae, which includes rats, mice, hamsters, gerbils, voles, and lemmings. Muridae is the largest family of mammals, with over 700 species. The common ancestor of Muridae lived about 16 million years ago in Asia.
From this ancestor, rats evolved into two main subfamilies: Deomyinae and Murinae. Deomyinae includes spiny rats and brush-furred mice, which are mostly found in Africa. Murinae includes true rats and mice, which are found worldwide. The first true rats appeared about 12 million years ago in Asia. They were larger and more adaptable than their relatives and soon spread across Eurasia and Africa.
Some of the earliest rat fossils have been found in China, India, Pakistan, Thailand, Indonesia, and Turkey. These fossils belong to genera such as Antemus, Diatomys, Karnimata, Progonomys, and Rattus. Rattus is the genus that includes most of the modern rat species, such as the Norway rat (Rattus norvegicus) and the black rat (Rattus rattus). Rattus originated in Southeast Asia about 4 million years ago.
Rats reached Europe about 3 million years ago, Australia about 1 million years ago, and America about 500 thousand years ago. They were able to colonize these continents by hitching rides on human ships or rafts, or by crossing land bridges during glacial periods. Rats adapted to various climates and environments, from tropical forests to arctic tundras. They also diversified into many different species and subspecies, such as the brown rat (Rattus norvegicus), the roof rat (Rattus rattus), the kangaroo rat (Dipodomys spp.), and the naked mole-rat (Heterocephalus glaber).
How rats adapted to different environments and cultures
Rats are remarkable for their ability to survive and thrive in almost any habitat and situation. They have developed various physical and behavioral traits that help them cope with different challenges and opportunities. Some of these traits are:
- Size: Rats vary in size from the tiny pygmy mouse (Mus minutoides), which weighs only 10 grams, to the giant Gambian pouched rat (Cricetomys gambianus), which can weigh up to 1.5 kilograms. Generally, larger rats live in colder regions, while smaller rats live in warmer regions. This is an example of Bergmann’s rule, which states that animals tend to be larger in colder climates to conserve heat.
- Fur: Rats have fur that covers most of their body, except for their ears, tail, feet, and nose. The color and texture of their fur depend on their habitat and camouflage needs. For example, desert rats have sandy-colored fur that blends with their surroundings, while forest rats have brown or black fur that matches the soil or vegetation. Some rats have spiny fur that protects them from predators or parasites, while others have soft fur that insulates them from cold or heat.
- Tail: Rats have long tails that serve multiple functions. They use their tails for balance when climbing or jumping, for thermoregulation when exposed to extreme temperatures, for communication when signaling to other rats, and for defense when fighting or escaping from enemies. Some rats have prehensile tails that can grasp objects or branches, while others have scaly tails that can shed skin when grabbed by predators.
- Teeth: Rats have four incisors, two on the upper jaw and two on the lower jaw, that grow continuously throughout their lives. They have to gnaw on hard materials, such as wood, bones, or metal, to keep their teeth from overgrowing and causing health problems. Rats use their teeth for various purposes, such as cutting, scraping, digging, or fighting. Their teeth are very strong and can bite through almost anything, including concrete, lead, and steel.
- Diet: Rats are omnivorous, meaning they eat both plant and animal matter. They have a very flexible and opportunistic diet and can consume almost anything that is edible or nutritious. They eat seeds, fruits, nuts, grains, vegetables, fungi, insects, worms, eggs, fish, birds, reptiles, amphibians, mammals, carrion, garbage, and even human feces. Rats can also survive without water for long periods of time by obtaining moisture from their food or from dew.
- Sociality: Rats are highly social animals that live in groups called colonies or packs. They communicate with each other using vocalizations, body language, scent marking, and grooming. They cooperate with each other in finding food, building nests, raising offspring, and defending territory. They also form bonds with each other based on kinship, friendship, or dominance. Rats can recognize individual rats and humans by their faces and voices.
- Intelligence: Rats are very intelligent animals that can learn from experience and solve complex problems. They have excellent memory and can remember routes, locations, objects, and individuals for long periods of time. They can also use tools, such as sticks or stones, to obtain food or escape from traps. They can even manipulate their environment to create favorable conditions for themselves or their group. Rats can also exhibit empathy, altruism, deception, and self-awareness.
Rats have not only adapted to different environments but also to different cultures. Rats have been associated with various human civilizations and societies throughout history. Some of these associations are:
- Ancient Egypt: Rats were revered by the ancient Egyptians as sacred animals. They were associated with the goddess Wadjet, who was depicted as a cobra-headed woman or a rat-headed woman. Wadjet was the protector of the pharaohs and the patron of lower Egypt. Rats were also linked to the god Ra, who was believed to create rats from his tears. Ra was the sun god and the king of the gods.
- Medieval Europe: Rats were despised by the medieval Europeans as pests and plagues. They were blamed for spreading diseases such as the bubonic plague (also known as the Black Death), which killed millions of people in Europe in the 14th century. The plague was caused by a bacterium called Yersinia pestis which was transmitted by fleas that lived on rats and other rodents. Rats were also associated with witchcraft and devilry. People believed that rats were familiars or servants of witches or demons.
- Imperial China: Rats were respected by the imperial Chinese as symbols of wealth and prosperity. They were associated with the god Daikoku (also known as Caishen), who was the god of fortune and abundance. Daikoku was often depicted as a smiling man with a rat on his shoulder or in his hand. He was one of the Seven Gods of Fortune in Chinese mythology. Rats were also linked to the zodiac sign of the Rat (also known as Shu), which is the first sign of the 12-year cycle. People born under this sign are said to be clever, charming, adaptable, and ambitious.
- Modern America: Rats are viewed by modern Americans as both pests and pets. On one hand, rats are considered as nuisances and threats that damage property and spread diseases such as leptospirosis (also known as Weil’s disease), which is caused by a bacterium called Leptospira that is excreted by rats in their urine. On the other hand, rats are also kept as domesticated pets by many people who appreciate their intelligence,
personality, and affection. Domesticated rats differ from wild rats in terms of appearance, personality, health, and lifespan. They come in various colors, patterns, and sizes. They are more docile, friendly, and curious than wild rats. They are less prone to diseases, parasites, and predators than wild rats. They live longer than wild rats, averaging 2 to 3 years compared to 1 year or less.
How rats became domesticated pets and scientific subjects
Rats have not only been living with humans but have also been used by humans for various purposes. Some of these purposes are:
- Entertainment: Rats have been trained and exhibited by humans for entertainment since ancient times. For example, in ancient Rome, rats were used for gambling and gladiator fights. In medieval Europe, rats were used for rat-baiting, a cruel sport where dogs were set to kill as many rats as possible in a pit. In modern times, rats are used for shows and competitions, such as agility, obedience, and trick contests.
- Companionship: Rats have been kept as pets by humans for centuries. The first recorded pet rat was owned by Queen Elizabeth I of England in the 16th century. She named it Hector and kept it in a golden cage. Pet rats became more popular in the 19th century, especially among the upper class and the artistic community. Some famous pet rat owners include Beatrix Potter, Mark Twain, Theodore Roosevelt, and Ernest Hemingway. Pet rats are affectionate, playful, and loyal animals that can bond with their owners and other pets.
- Research: Rats have been used as scientific subjects by humans for over a century. They are ideal for research because they are easy to breed, handle, and manipulate. They also share many physiological and genetic similarities with humans. Rats have contributed to many scientific discoveries and advancements, such as the development of antibiotics, vaccines, organ transplants, cancer treatments, and behavioral studies. Rats are also used for ethical and educational purposes, such as animal rights advocacy and biology teaching.
- Conservation: Rats have also been used as conservation agents by humans in recent years. They are trained to detect landmines, explosives, and other hazards that pose threats to wildlife and human lives. They are also trained to sniff out endangered species, such as pangolins, elephants, and rhinos, that are illegally hunted or traded. Rats are suitable for these tasks because they have a keen sense of smell, a low weight, and a high intelligence. They can work faster and safer than dogs or humans.
Conclusion
Rats are amazing animals that have a rich and diverse history and evolution. They have evolved from ancient rodents to modern mammals that can adapt to any environment and culture. They have also been used by humans for various purposes, such as entertainment, companionship, research, and conservation. Rats have influenced our history, culture, science, and health in many ways. They deserve our respect and appreciation for their remarkable role in our world.
I hope you enjoyed reading this article about the history and evolution of rats. If you did, please share it with your friends and family who might be interested in learning more about these fascinating creatures. Thank you for your attention and support!
